Process for preparing cyclopropane



, V Patented Aug. 3, 19 43 I 1 2,325,591 PROCESS For: ranranrnc CYCLOPROPANE Walter GLChristiansen, Glen mag iv. 1., and John M. Ort, Rockville Centre, N. Y., assignors to E R1 Squibb.& Sons poration 01' New York New York, N. Y., a cor- No, Drawing. Application October 9, 1941, l

Serial No. 414,354 r t 7 Claims. (cl. 260-666) This, invention relates to the: preparation of cyclopropane has heretofore been prepared by 1 the reaction of trimethylene dihalides with finelydivided metalreduction agents in various liquid 1 reaction media (in which the metal is suspended i and the dihalide is more or less dissolved), e. g.,,

by thereaction of trimethylene dibromide with zinc dust inaqueous ethanol. Whilethis procedure has been developed to a high state of rise to 'certain complications, inter alia, thej (economic) necessity of recovering the medium if essentially alcoholic, and the occurrence or side reactions due to or involving the medium.

It is the object of this inventionto provide an 4101 efficiency, the use of liquid reaction'media gives.

methylene dibromide in lieu o f-trimethylene dichloride inthe foregoing example, gives even better results; inasmuch astheyare more reactive than the dichloride and hence do not require as high a reaction temperature, and the use of lower temperatures minimizesundesirable side reactions and increases :the yield.

Magnesium or other metal reduction agents: may be used in lieu :of the zinc in -the foregoing example; the pipe and the electric furnace reactor may be replaced by flame-heated charged improved process oi preparing cyclopropane which does not require the use of a liquid reaction medium.

i The process of this invention essentially comprises contacting the vapor of a trimethylene dihalide with a metal reduction agent. The invention is, applicable generally to the production, of i cyclopropane by the reduction of trimethylene dihalides; thus, the preferred trimethylene dihalides, are the dibromide, chlorobromide, and;

dichloride, and the utilizablej metal reduction reaction is favoredbyoperatingat elevated ternperatures, which may beas high as about 500 C.; but a" temperature of about 200-300 C. is

optimal from the standpoint ofobtaining a rea-,

sonably rapid reaction with a minimum of charring. The reaction, is also favored by higher surface-volume ratio in the ,metal reduction 1; agentfhencef the agent ispreferably used in an extended-surface form, inter all-a, wire, granule,

powder, or dust form. e i

The following example is illustrative oithe in- V vention: A metal (e. g.,bronze) pipeis charged with zinc dust and placed in an electric furnace maintainedat about 200-300" C. ,Tri'methylene agents include zinc, sodium,and magnesium. The

dichloride vapor is then passed through the zinc clo'propane (based on the reacted trimethylene dust until the surface of the zinc becomes caked I, andinactivated. An about 50-60% yield of cydichloride) is obtained; and the unreacted trimethylene dichloride condensed "from thefemerginggases is returned to the reaction.

I The ca'ked-or coated zinc powder is reactivated I bywashing with water} filtering, and dryingand I used {or recharging the pipe.

1 The use of trimethylenechlorobromide or tri glass tubes or any other suitable reactors; and the length of the hot zone in the pipe, the speed of the vapor addition, and the quantity of metal; 1 reduction agentin the pipe may be varied within u wide limits. Preferably, however, the quantity of metal reduction agent is greatly in excess of that required for reaction with the. quantity of dihalide used. i I

The invention may bevariously otherwise em-. bodied, within the la m v r 1. i The process of preparing cyclopropane which comprises passing the vaporof a trimethylene di halidethrough a reactor charged with a metal reduction-agent. i

i 2; The process of preparing cyclopropane which g comprises passing the vapor of a trimethylene dihalide through'a heated reactor, charged with a" metal reduction agents 3. The process of preparing cyclopropane which I comprises passing the vapor of a trimethylene dihalide through a reactor charged with zinc. 4. The process of preparing cyclopropane which comprises passing the vapor of trimethylene dichloride througha reactor-charged with a metal I 1 l 7 reduction agent.

, 5. The process of preparing cyclopropane which comprises passing the vapor of a trimethylene dihalide through a reactor charged with a metal reduction agent and heated to about200-300" C.

V 6. The process of preparing cyclopropane which comprises passing the vapor of a trimethylene dihalide throughja reactorcharged with a metalj reduction agent in an'extended-surfac form.

7. The process" of preparing cyclopropane which 3 comprises passing the vaporof-a trimethylene di- P halide through 'a reactor charged'with a metal reduction agent in an extended-surface form and heated to about zoo-300 c. e

WALTER oHms'rIANsEN.

7 'JOHN 012.11.

scope of the appended claims. 

